Phosphorus Loss through Overland Flow and Interflow from Bare Weathered Granite Slopes in Southeast China

Abstract

Phosphorus (P) is the key limiting factor for eutrophication, and the mechanism of P loss from hillslopes is complex. Few attempts have been made to study the processes of P loss through overland flow and interflow from bare weathered granite slopes in Southeast China. Therefore, artificial rainfall simulations were performed to evaluate P loss from bare weathered granite slopes with different slope angles (5°, 8°, 15°, 25°) and different rainfall intensities (1.5, 2.0, 2.5 mm/min). The results show that overland flow increased with rainfall intensity, while it declined with slope angle. Interflow exhibited a single-peak curve with time of runoff. The interflow accounted for 28.53–89.12% of the total runoff yield, and the percentage declined with rainfall intensity and increased with slope angle. Both total phosphorus (TP) concentration (CTP) and TP load (LTP) in overland flow increased with rainfall intensity, and the percentages of LTP in each rainfall event ranged from 51% to 92%. CTP in overland flow distinctly fluctuated, with the maximum appearing on the 25° slope, while the maximum in interflow was observed on the 5° slope. LTP in overland flow was the highest on the 8° slope, and was significantly affected by runoff yield and rainfall intensity (p < 0.01). LTP in interflow was small and was significantly affected by rainfall intensity (p < 0.01). Runoff P was mainly lost through overland flow, dominantly in the form of particulate phosphorus (PP), and P loss through interflow was an important supplementation, mainly in the form of dissolved phosphorus (DP). These results provide underlying insights and scientific background for the control of P loss in bare weathered granite areas.

Water and nutrient balances under selected soil and water conservation practices in semi-arid Ruzizi plain, Eastern Democratic Republic of Congo

“…Tied ridges significantly reduced nitrogen and phosphorus losses compared to the Zaï pits. This performance is associated with this SWC practice ability to reduce the surface runoff and downward drainage (Ngetich et al, 2014;Deng et al, 2019). We also observed a strong relationship between the runoff, drainage amount and the total nitrogen losses (p<0.01) as opposed to the phosphorus losses that were only associated with the runoff.…”

“…Li et al (2015) reported that the P loss is mainly caused by loaded sediments in the runoff, while it is relatively low in the subsurface flow. Other studies observed that the amount of runoff and sediment increases with the slope gradient and rainfall intensity (Fu et al, 2016;Deng et al, 2019). It is noteworthy that nutrient losses by runoff tended to decrease toward the end of the cropping season.…”

A Reliable U-trough Runoff Collection Method for Quantifying the Migration Loads of Nutrients at Different Soil Layers under Natural Rainfall

“…Huang et al [35] used these troughs at the runoff flume's down-end to collect SSR in the laboratory. Zhu [3], Deng et al [36][37][38], and Wang et al [39][40][41] adopted the conflux troughs at the lower end of the sloping land to collect SR and SSR in field runoff plots. The collected runoff was then introduced into the runoff storage bucket by water pipes [42].…”

Adsorption of nitrate from interflow by the Mg/Fe calcined layered double hydroxides

“…NO 3 -N is the main form of N loss, with the average concentration varying from a few to dozens mg/L (Wang & Zhu 2011;Chu et al 2020). However, the generation of interflow is hard to evaluate due to many uncontrollable factors, such as rainfall intensity and duration, land use patterns, soil properties and vegetation cover (Deng et al 2019). Therefore, the generation of interflow is intermittent, and the concentration as well as the total amount of NO 3 -N in interflow is variable.…”